After playing around with both Steam and PaintShop Pro recently, I have found a 'Fix' for an issue where PaintShop Pro was not able to see any Screenshots in the Steam-created Screenshot Folders, when trying to "Browse" within PaintShop Pro... Here is what it looks like in PaintShop Pro when trying to "Browse" to a Steam Screenshot Folder within the graphic editing application itself:

As seen above, the Browsing utility in PaintShop Pro says "No Files Found" [circled in Red] - but obviously there are files/images in the folder, as opening the same folder with Windows Explorer just below it (Windows 10) shows there are tons [I take way too many Screenshots, heh]

I examined the Properties of the Screenshots generated by Steam, but they are nothing out-of-the-ordinary, they are typical .JPG (JPEG format) image files. 
PaintShop Pro is able to "Browse" other folders I have with Screenshots, so perhaps it had something to do with Permissions [was my thinking]...
I ran PaintShop Pro as Administrator, but it seemed to make no difference. 
I then examined the Preferences of PaintShop Pro. I have been in there before, to change some of the behaviour of the editing program, namely Caching and Colour Correction/Import and Precise Cursors [I really prefer the Precise Cursors, I Recommend using them!]

In PaintShop Pro's Preferences, I found there are some Exclusions that were already in the program [built-in, on install] that, while helpful, interfered with where Steam keeps game Screenshots by Default.

These Exclusions, in PaintShop Pro, are located in:

File > Preferences > General Program Preferences 

In the Manage category, Excluded Items section, there is a button for Uncataloged Folders.

[These folders are not utilized by PaintShop Pro, and while I'm not sure why, I assume it is because they are large System Folders and may result in duplicates or 'garbage' images being read, which would take up time and excessive space for Thumbnails]

In these "Uncataloged Folders", I found a listing of
C:\Program Files
and Steam itself is installed (by Default, in Windows) to
C:\Program Files (x86)

It appears that PaintShop Pro thinks that "Program Files (x86)" is part of, or is, "Program Files" [due to the space in the former] - so it excludes that folder from use; thus, it is not possible to Browse those folders with PaintShop Pro [was my thinking].

Removing the "C:\Program Files" from the Uncataloged Folders, I tried to open a game's Screenshots Folder (unchanged, where Steam normally keeps them by Default) with BROWSE in Paintshop Pro...

It worked! 😁

That was it then - it appears removing that Folder (C:\Program Files) from the Uncataloged Folders category, is all that needs to be done and Paintshop Pro can then Browse and Catalogue [create Thumbnails for] those Folders.

In the image I created just below, there is an open Steam Screenshots Folder in the background, showing that Steam's Screenshot Folders indeed now work with PaintShop Pro.

Here is a large collage/screenshot showing what I found and how to change it [It looks a little busy/crazy - so I will explain it just underneath, heh]:

In the 'Tutorial' image above, I have indicated the following areas below on how to 'fix' this issue with PaintShop Pro:

» The Large 'Green Arrow' shows that I have a Steam Screenshot Folder open in the Browse/Manage are of PaintShop Pro [It now works! There are Screenshots seen in the background middle workspace] 
» The Smaller 'Yellow Arrows' are indicating the 'trouble folders' of "Program Files" and "Program Files (x86)" that PaintShop Pro seems to have issue with [These folders, generated automatically by Windows, hold most Programs and installed Applications. The 'x86' Folder is generally used for backwards-compatibility with older (32-bit) Programs] 
» The Red 'Roman Numerals' (I., II., etc.) indicate the Steps To Take to navigate to the "C:\Program Files" listing in the "Uncategorized Folders" section of the Excluded Items in PaintShop Pro 
» The Red 'Information Icon' is simply the Panel that must be opened, using these Steps, to see/edit the Folders to be discluded from the "Browse" capability of PaintShop Pro

Here are the Tutorial Steps, in order, to remove this Exclusion and allow PaintShop Pro to Browse/Manage Steam Screenshot Folders and Images:

  1. Click on "File"
  2. Select "Preferences"
  3. Go into "General Program Preferences "
  4. Click on the "Manage" section on the left of the Preferences panel that comes up
  5. In the "Excluded Items" section on the right, click on the button for "Uncataloged Folders"
  6. In the "Uncataloged Folders" panel, select the "C:\Program Files" listing and click on the Delete button
  7. Click Ok, above the Cancel button
  8. Click Ok, to close the Preferences Panel
  9. You are now back at the main PaintShop Pro interface

That's it!

Hopefully this finding can help others that want to use Paintshop Pro with Steam Screenshots, now easily Browsing them all (with Thumbnails being Cached for faster access/listing) with PaintShop Pro.

Hope That Helps!

~ Troy from The Game Tips And More Blog

[Note: I am not affiliated with Corel or Steam/Valve, and have not, and will not, receive any compensation in any form, for mentioning them here. I am merely an enthusiastic gamer who utilizes their products, and likes to share helpful information for others when I can]